Accessible and Informative Sectioned Images, Color-Coded Images, and Surface Models of the Ear

Authors


Correspondence to: Jin Seo Park, Department of Anatomy, Dongguk University College of Medicine, 87 Dongdae-ro, Gyeongju, Republic of Korea 780-350. Fax: +82-54-770-2402. E-mail: park93@dongguk.ac.kr

ABSTRACT

In our previous research, we created state-of-the-art sectioned images, color-coded images, and surface models of the human ear. Our ear data would be more beneficial and informative if they were more easily accessible. Therefore, the purpose of this study was to distribute the browsing software and the PDF file in which ear images are to be readily obtainable and freely explored. Another goal was to inform other researchers of our methods for establishing the browsing software and the PDF file. To achieve this, sectioned images and color-coded images of ear were prepared (voxel size 0.1 mm). In the color-coded images, structures related to hearing, equilibrium, and structures originated from the first and second pharyngeal arches were segmented supplementarily. The sectioned and color-coded images of right ear were added to the browsing software, which displayed the images serially along with structure names. The surface models were reconstructed to be combined into the PDF file where they could be freely manipulated. Using the browsing software and PDF file, sectional and three-dimensional shapes of ear structures could be comprehended in detail. Furthermore, using the PDF file, clinical knowledge could be identified through virtual otoscopy. Therefore, the presented educational tools will be helpful to medical students and otologists by improving their knowledge of ear anatomy. The browsing software and PDF file can be downloaded without charge and registration at our homepage (http://anatomy.dongguk.ac.kr/ear/). Anat Rec, 2013. © 2013 Wiley Periodicals, Inc.

INTRODUCTION

Human ear structures are hardly accessible by both cadaver dissection and microscopy; most learning tools for displaying the complex anatomy of the ear have been limited to plastic models for several decades. To escape this limitation, researchers have developed new learning tools, consisting of three-dimensional (3D) models (Wang et al., 2006, 2007; Li et al., 2007; Sorensen et al., 2009; Phillips et al., 2012). For that, basic image data were obtained by anatomists or clinicians, while software packages, on which the processed images are explored, were developed by computer engineers.

Our Visible Korean project team produced the exceptional ear data as follows. In sectioned images of a cadaver head (Park et al., 2009, 2010b), ear images (voxel size, 0.1 × 0.1 × 0.1 mm3; color depth, 48-bit color) were selected, and color-coded images displaying 31 segmented ear structures were elaborated. Based on the color-coded images, surface models were built on Maya version 2009 (Autodesk, Inc., San Rafael, CA). From this ear data, both macroscopic (e.g. cochlear duct and semicircular duct) and microscopic structures (e.g. tensor tympani muscle, stapedius muscle, and chorda tympani) could be observed in detail (Jang et al., 2011). However, our ear data were not easily accessible because application software was not presented. Namely, the sectioned images could not be browsed along with accompanying color-coded images; the surface models could be operated only on Maya, which is very expensive and complicated software. Therefore, we tried that our data were applied to ear software of other research group such as visible ear of Massachusetts Eye and Ear Infirmary (http://otopathologynetwork.org) and A Brown and Herbranson Imaging Company (http://ehuman.com); but we did not success because they were completion software, not allowing modification or supplement by not-computer engineer.

Meanwhile, we have already released browsing software in which the common user can easily access and browse sectioned images of the complete male body (Shin et al., 2011b) and a cadaver head (Shin et al., 2012c). Further, we have demonstrated that the free software package Adobe Reader Windows version 9 (Adobe Systems, Inc., San Jose, CA) can display surface models of the complete male body and a cadaver head in a portable document format (PDF) file (Shin et al., 2012b, 2012c).

The purpose of this research was to distribute the browsing software and the PDF file of ear, on which sectioned images, color-coded images, and surface models of detailed ear structures can be accurately explored, thereby making ear anatomy easier to learn. Another goal was to inform other researchers of our methods for establishing the applications; eventually to enable the medical experts to better utilize their own specialized 2D and 3D data. To achieve these goals, the sectioned images and color-coded images of the right ear were updated, and those images and surface models were put into the browsing software and PDF file, respectively.

MATERIALS AND METHODS

In a previous study, our research team produced sectioned images of a cadaver head (number, 2,341; resolution, 4,368 × 2,912; voxel size, 0.1 mm; color depth, 48-bit color; file format, tagged image file format (TIFF)) (Park et al., 2009, 2010b). From those, sectioned images of the ear region were selected (number, 221; resolution, 1,622 × 420; voxel size, 0.1 mm), then primary color-coded images of 31 ear structures were produced (number, 221; resolution, 1,622 × 420; voxel size, 0.1 mm) on Photoshop CS5 version 12 (Adobe Systems, Inc., San Jose, CA) (Table 1; Jang et al., 2011).

Table 1. Thirty-one structures of the right ear segmented in sectioned images and reconstructed to build surface models
RegionStructures
  1. a

    Structures for hearing.

  2. b

    Structures for second pharyngeal arch.

  3. c

    Structures for first pharyngeal arch

  4. d

    Structures for equilibrium.

  5. e

    Structure for which the surface models were not reconstructed.

External earSkin, external acoustic meatus, tympanic membranea
Middle earTympanic cavity, oval windowa, stapesab, incusac, malleusac, tensor tympani musclec, stapedius muscleb, auditory tube
Internal earAnterior semicircular canalde, posterior semicircular canalde, lateral semicircular canalde, cochleaae, internal acoustic meatus, utricled, sacculed, anterior semicircular ductd, posterior semicircular ductd, lateral semicircular ductd, cochlear ducta
OtherOccipital bone, temporal bone, internal carotid artery, superior petrosal sinus, brainstem, facial nerve, chorda tympani, vestibular nerved, cochlear nervea

In the sectioned and primary color-coded images of ear, the left half was cut off (resolution, 811 × 420) (Figs. 1A,B and 2A). In the primary color-coded images of the right ear, hearing and equilibrium structures were colored blue and red, respectively. Except for the blue and red structures, chroma of the remnant structures was reduced to create the secondary color-coded images (Figs. 1C and 2A; Table 1). In the primary color-coded images, structures originating from the first and second pharyngeal arches in the embryo stage were colored (first pharyngeal arch, blue; second pharyngeal arch, red) to prepare the tertiary color-coded images (Figs. 1D and 2A; Table 1).

Figure 1.

Sectioned and color-coded images of the right ear which were viewed from below. Sectioned images (A; row), primary color-coded images (B; row), secondary color-coded images (C; row), and tertiary color-coded images (D; row) in upper (E; column) and lower (F; column) levels around the middle ear. In the secondary color-coded images (C; row), blue and red colors signify hearing and equilibrium structures, respectively. In the tertiary color-coded images (D; row), blue and red colors originate from first and second pharyngeal arches in that order.

Figure 2.

Browsing software and PDF file of the right ear. Using the browsing software, sectioned images along with accompanying primary, secondary, and tertiary color-coded images of the not cropped ear (A) as well as the cropped ear (B) are shown from below. Furthermore, the name of each structure is displayed when the mouse pointer floats over a specific structure (A and B). PDF file is composed of a model tree window, bookmark window, and surface models window (C).

Margins in all images, beyond for the middle and internal ears, were simultaneously cut off to obtain the cropped ear (resolution, 406 × 210) (Fig. 2B).

Previously, browsing software was developed in order to explore the sectioned and color-coded images of cadaver head using the C# language of Microsoft Visual Studio. NET 2003 (Microsoft Corporation, Redmond, WA) (Shin et al., 2011b, 2012c). The software was composed of operating and image files that were replaced with our new data: not cropped ear and cropped ear in sequence. The operating and new image files were transformed into Browsing[lowem]software[lowem](Male[lowem]ear).exe, which was installation file, on the Nullsoft Scriptable Install System of NSIS Media.

The ear surface models were built from the primary color-coded images of bilateral ears and saved as stereolithography (STL) files on Maya (Jang et al., 2011). On Maya, the surface models of bilateral ears were divided into left and right structures except brainstem and occipital bone. Using the Right Hemisphere Deep Exploration Standard (San Ramon, CA), STL files were categorized into right and left parts: external ear (right), external ear (left), middle ear (right), middle ear (left), internal ear (right), internal ear (left), other (right), other (left), and other (bilateral). In each part, the surface models were arranged in official anatomical terms (Table 1; FCAT, 1998). After finishing the coordination, all models in the STL files were gathered and saved as Male[lowem]ear.pdf using the 3D Reviewer, accompanying software of Acrobat 9.0 Pro Extended (Adobe Systems, Inc., San Jose, CA) (Shin et al., 2012b2012c). When the PDF file was opened on Adobe Reader, the anatomical terms of the parts were displayed in the model tree window (Fig. 2C).

To learn anatomy, it was advantageous that models were assembled according to region. Thus, each region was assembled to be in bookmark window of the PDF file on Acrobat as follows: bilateral ear (anterosuperior view), right ear, right ear without temporal bone, hearing ear, equilibrium ear, first pharyngeal arch ear, and second pharyngeal arch ear (Fig. 2C; Table 1).

A previous article published in the Anatomical Record journal explaining the sectioned images and surface models of the ear (Jang et al., 2011) was attached in the PDF file. Page 1 was already occupied by ear surface models, so the article was included in the remaining pages.

RESULTS

The browsing software (253 MB) and PDF file (50.5 MB) can be downloaded without charge or registration at the homepage of the Department of Anatomy, Dongguk University College of Medicine (http://anatomy.dongguk.ac.kr/ear/).

In the browsing software, only right ear could be shown because it was programmed based on the right side. In the PDF file, right, left, or bilateral structures could be shown like bookmark window because it was built from images of bilateral ears.

After installing the browsing software by one-clicking the EXE file, the sectioned images along with three sets of accompanying color-coded images could be easily browsed in real-time. The user was able to select the images either by using the scroll bar or by typing an image number into the software. The neighboring images were continuously displayed by clicking the tools in the software. When the user placed the mouse pointer over a structure in the sectioned or color-coded images, its name appeared as a tool tip text (Fig. 2A,B).

Next, ear surface models in the PDF file were explored on Adobe Reader version 9 and higher. The surface models could be suitably zoomed-in or zoomed-out, as well as freely rotated and shifted using mouse drag with its buttons pushed. The surface models could be made semi-transparent in order to view the back structures of the models. When the user clicked a model, its structure name was highlighted in the model tree window. Clicking structure names in the model tree window prompted the appearance of matching surface models either individually or by group (Fig. 2C).

Ear anatomy could be easily comprehended by observing sectional planes on the browsing software and 3D shape on the PDF file. Examples are as follows.

In the sectioned and primary color-coded images on browsing software, the incus was located between the malleus and the stapes. The stapes fitted into an oval window at the medial wall of the tympanic cavity, and it was connected with the cochlea through the oval window. In a sectioned image, a few holes of the spiral cochlea were shown. By these considerations, the user could understand the sectional shape of the hearing structures (Figs. 1A,B and 3A,B). For more convenience, the structures related to hearing could be verified independently in the secondary color-coded images (Fig. 1C). The tertiary color-coded images were supplementary to help comprehend the embryonic origins of these structures.

Figure 3.

Sectioned image, primary color-coded image, and surface models of right middle and internal ears with annotations. Real sectional shapes of structures around ear ossicles are shown from below in sectioned images (A), and positional relationships of the structures can be comprehended based on color in the primary color-coded images (B). Real three-dimensional shape of ear ossicles and cochlea are shown (C).

In the PDF file, the tympanic membrane displayed concavity toward the external acoustic meatus as the tensor tympani muscle medially pulled the tympanic membrane through the embedded the malleus handle. The rounded superior head of malleus was articulated with the large body of incus. The long limb of incus lied parallel to the malleus handle, and its interior end encountered with the stapes. The spiral cochlea made 2.5 turns around a bony core, where cochlear nerve anchored. The large basal turn of the cochlea produced the promontory of the tympanic cavity (Fig. 3C).

Using the browsing software, the holes of the anterior and posterior semicircular ducts were observed. Although the user could expect that the ducts were right-angled, it was unclear in a sectional view (Fig. 4A). In the PDF file, the user could accurately observe that the two ducts formed a right angle with the common membranous crus as the center. The lateral semicircular duct was smaller than other ducts (Fig. 4B,C).

Figure 4.

Semicircular ducts in sectioned images and surface models of the right ear. Anterior and posterior semicircular ducts are at right angles in a sectioned image (A), superior view of right ear surface models (B), and lateral view of left ear surface models (C), as indicated by the red line and arrow.

In the PDF file, the tympanic membrane was observed through virtual otoscopy. The right-sided membrane was divided into four quadrants: anterosuperior (I), anteroinferior (II), posteroinferior (III), and posterosuperior (IV). The malleus handle was criteria intervening between quadrants I and IV, and the umbo was meeting point of four quadrants. The quadrants are clinically important as they are used to describe the locations of lesions. For example, quadrant II shows the location of “cone of light,” which is helpful in determining the tension of the tympanic membrane (Fig. 5A). In succession, virtual tympanoplasty was performed and the results compared with those of real surgery. After removing tympanic membrane, in the superior part of quadrant IV, long limb of the incus and chorda tympani could be seen. The chorda tympani, originating from the facial nerve, crossed between the malleus and incus (Fig. 5A). The anatomical and clinical knowledge in the PDF file were identical to that of a textbook (Fig. 5B; Clemente, 1).

Figure 5.

Virtual and real otoscopy of the right ear. After the tympanic membrane is removed and opacity of temporal bone is adjusted semitranslucently in the PDF file, the membrane is divided virtually into four quadrants. Shape of ear structures can be verified regardless of their locations (A). At the same location, only the tympanic membrane and some folds can be observed by real otoscopy, presented by a textbook (B; Clemente, 2010).

DISCUSSION

In our previous research, we created state-of-the-art scientific sectioned images as well as surface models of the ear (Jang et al., 2009), whole body (Park et al., 2005a, 2005b, 2007, 2008; Shin et al., 2009a, 2009b, 2012a, 2012d), head (Park et al., 2009, 2010a, 2010b; Shin et al., 2011a), and pelvis (Hwang et al., 2010). We expected that our data could be applied by computer engineers, but this did not happen; as a result, our data were not informative since there was no easily accessible application developed. Therefore, we tried to create the products of our data by ourselves; finally in this research, we presented the outcomes which consisted of the browsing software for sectioned images and the PDF file for surface models of ear.

Our developed browsing software and PDF file of ear are easily obtainable. On the installed browsing software, the sectioned images along with accompanying color-coded images can be conveniently browsed using the mouse or keyboard, and names of the structures can be displayed by placing the mouse pointer over the images (Fig. 2A,B). Further, the PDF file can be viewed for free on Adobe Reader. In the PDF file, surface models of each structure can be selected, rotated, zoomed-in, and zoomed-out freely using the mouse (Figs. 2C, 3C, 4B,C, and 5A).

Users must be able to easily access the applications, as mentioned above; however, more importantly, accurate knowledge of anatomy should be obtainable from the informative applications. The sectioned images display accurate anatomical information as they were made directly from the human body. The color-coded images and surface models are also precise, as they were created based on the sectioned images. In the browsing software and PDF file, not only the sectional plane but also the 3D shape of each structure can be observed and names of the structures can be displayed as they were built form the sectioned and color-coded images (Figs. 2-4). Therefore, users can acquire literal anatomical knowledge of the ear using our applications. In clinics, an otologist has to interpret the computed tomographs of head to identify the ear components (Stimmer, 2011; Phillips et al., 2012). The browsing software and PDF file could be utilized as the reference images.

Our applications can meet the demands of various scientific fields through upgraded or altered color-coded images and surface models. In ear physiology, structures related to hearing and equilibrium are very important. Thus, these structures were included in the secondary color-coded images and a bookmark in the PDF file. In ear embryology, structures originating from the first and second pharyngeal arches were involved in the tertiary color-coded images and another bookmark also (Figs. 1 and 2). A textbook explanation about the ear could be inserted in the PDF file. Likewise, we hope that users or other researchers will promptly build the browsing software and PDF file according to their purposes

To prove the objectivity of our surface models, we performed virtual otoscopy and tympanoplasty. As a result, our PDF file could be applied as training tool in otology as follows: using the PDF file, an otologist sees the tympanic membrane with its folds in quadrant IV and he/she virtually removes the tympanic membrane. The doctor verifies that the malleus handle as well as chorda tympani are located inside of tympanic membrane's folds. In the four quadrants of the membrane, it is proved that quadrant II is safest zone because no one is very close inside the quadrant II. In addition, the doctor can observe other structures in the middle and internal ears (Fig. 5A). If it is real otoscopy, the tympanic membrane and the some folds can be only observed, whereas the chorda tympani and its related structures behind the tympanic membrane are not observed. It is difficult to realize the location of structures behind the tympanic membrane in quadrant IV and II (Fig. 5B). Without virtual otoscopy and tympanoplasty, the resident is trained by the recorded real practice movies or illustrations that are not interactive and stereoscopic (Marchioni et al., 2011). Therefore, in a way, virtual otoscopy and tympanoplasty using the PDF file can be more informative although the data are not yet sufficient for use in a clinical setting. Accordingly, we hope that the virtual simulation is improved by other researchers not only using our scientific data but also adding other objective contents such as visible ear of Massachusetts Eye and Ear Infirmary (http://otopathologynetwork.org).

Junior doctors of otology as well as most medical students find ear anatomy difficult when only non-interactive tools such as textbooks, plastic models, and recorded dissection movies are available for learning. They feel uncomfortable with otoscopy and tympanoplasty of patients because it is known how difficult and dangerous the practices are. Our applications will be able to solve somewhat the uncomfortable feeling because most ear structures can be observed in detail with real color using personal computer-based, off-line, interactive environment in our applications (Figs. 1-5); furthermore, they can be accessed and used easily free of charge. Our developed applications can be easily upgraded according to the needs of researchers. The browsing software and PDF file will be helpful to medical students and otologists by improving their knowledge of ear anatomy.

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